Temperature stable ink transfer coating compositions



United States Patent O US. Cl. 117235 19 Claims ABSTRACT OF THEDISCLOSURE An ink transfer coating composition of improved temperaturestability comprising a pigment dispersed in a resin, a plasticizer and asolvent system compatible with the resin. Low viscosity resins arepreferred. The pigment may be finely divided rnagnetizable particles.Specific resins, solvents, and plasticizers are included, as well assurfactants.

FIELD OF THE INVENTION Compositions of matter, having or not havingstructure, physical form or heterogeneous arrangements of components,including those designed for use as magnetic materials and for impacttransfer printing.

PRIOR ART Physical image transfer media such as typewriter ribbons andduplicator stencils are commonly used to transfer a visual image fromone medium to another. Each of these transfer media comprises asupporting base of paper or plastic foil, for example, carrying acoating of a pigmented material. For certain applications it isdesirable that the coating composition contain a magnetizable medium sothat the printed image in turn will be responsive to magnetic detectingmeans. With the increasing use of computers, for example, that have anability to read printed matter by optical and by magnetic means, qualitytransfer coatings become of increasing importance.

Current image transfer coatings as commonly used in the form oftypewriter ribbons, or print ribbons in high speed printers, suffer fromvarious inherent disadvantages. It is not unusual for these coatings tocontain 8 or 9 or more individual constituents. Many of theseconstituents are natural fats, oils, or greases, which are subject tothe variations that are inherent to any product from a natural source.Many of these coatings show a degradation of print quality when exposedto environmental conditions exceed, for example, 120 F. for periods oflonger than 24 hours. Thus storage of print medium utilizing suchcompositions often requires temperature and humidity control, both instorage and in shipment.

To compensate for some of these problems, the coating composition, whichis usually applied to an inert backing, such as polypropylene,polyethylene, Mylar, or other plastics or paper backings, is oftenapplied as a thick coating. This limits the number of feet of, forexample, typewriter ribbon, that may be wound on a given reel. Further,the thicker the coating, the more expensive it is to use, as a givenquantity coats less backing material. Current compositions also sufferfrom a lack of batch to batch uniformity, which reflects in part the useof natural materials. Handling of ink transfer coated tapes is oftenmessy, resulting in a transfer of the coating composition onto themechanical parts of the transfer unit, such as the rollers in a printingunit. This, of course, is clearly undesirable.

Thus it is desirable to produce an ink transfer coating ice compositionthat can be applied by current methods; on substrates currently in use;having better batch to batch uniformity; that are less expensive; areclean to handle; contain fewer components, and preferably of syntheticmaterials; and that offer a better print quality than is currentlyavailable. Such a composition should also lessen peeling or flakingproblems from the environmental storage and use of such tapes, and haveimproved release characteristics, that is, the ease of transference fromthe backing to the object printed upon.

SUMMARY OF THE INVENTION The present invention overcomes these and otherproblems of the prior art by formulating ink transfer compositionshaving superior release characteristics and improved temperaturestability when applied upon a plastic or paper backing material, forexample. These compositions include, in one case, a cellulose acetatebutyrate resin, a plasticizer, such as dioctyl azelate, a solvent, suchas N-propyl acetate, and a pigment dispersed therein, such as carbonblack or finely divided magnetizable iron oxide. Alcohol solublebutyrate and cellulose acetate propionate may also be used as the resin,with an appropriate plasticizer and solvent. Composition ranges andmaterials, and the advantages of these, will be evident from thefollowing objects and general description.

It is an object of this invention to formulate ink tnansfor coveringcompositions of improved environmental stability that suffers nodegradation of print quality in the temperature range of from --20 F. toat least F., even when stored under such conditions for a periodexceeding five days.

Another object is to formulate ink transfer coating compositions havingimproved print quality over those compositions of the prior art.

A further object is to formulate ink transfer coating compositions thatmay be applied to an inert substrate in a thinner layer than iscurrently done, thus reducing the cost of the final product, andincreasing the amount of such tape that may be stored on standard reels.

Still another object of this invention is to formulate ink transfercoating compositions comprised entirely of synthetic components,resulting in improved batch to batch uniformity.

A further object is to formulate ink transfer coating compositions ofimproved stability, resulting in a lessening of peeling or flaking ofthe composition from the backing than is found in the prior art.

A further object is to formulate magnetic ink transfer coatingcompositions incorporating the improvements of the aforementionedobjects.

GENERAL DESCRIPTION We have found that the resins cellulose acetatebutyrate, alcohol soluble butyrate, cellulose acetate propionate, ortenth-second butyrate, when combined with certain other materials, allsynthetic in nature, results in an ink transfer coating composition thatallows us to achieve the objects stated above. These compositions aremixed in the usual manner known in the art, and may be mixed in small orlarge quantities without any change in the resulting properties. Theresulting compositions may then be applied to a backing material by anyconventional coating technique, such as spraying, or screening, althoughwe have found the preferred process is to use the well known reverseroll process for applying the composition to the backing material.

While many backing materials may be used, such as Mylar, orpolypropylene, we have found it most desirable to use high densitypolyethylene. The coatings are generally, though not necessarily,applied to a backing of web form, and then cut into ribbons of anydesired width by means of conventional slitting machinery. Thus thecompositions of our invention have all the advantages of being able tobe used with conventional and well known processes of manufacture.

The resins used contain varying percents of aectyl, butyryl, andhydroxyl, and are generally classified by their viscosity using theA.S.T.M. falling ball viscosity test.

The following table, Table I, lists the various resins we have used bythe vendor code, in this case those products made by the EastmanChemical Products Co., the constituents therein, and lastly, the maximumviscosities of each resin that We desire to use in keeping with our Insome of our formulations, we have also found it desirable to use asurfactant or Wetting agent. We have found a surfactant comprising fattyamides plus polyethylene glycol ester, such as Tenlo '70, made by theNopco Chemical Company, to be especially useful. However, othersurfactants may be used.

Plasticizers are generally added to resins to impart flexibility andease of processing. The plasticizers must, of course, be compatible withthe resin with which they are to be used. Various plasticizers may beused in formulating the compositions of our invention.

Various solvents may also be used that meet the general requirementsthat the solvent or solvent system must dissolve the resin system usedin the formulation, and the solvent to resin system, from a practicalviewpoint, must evaporate at a rate which permits good coatingtechniques. The preferred solvents are listed with the preferredcompositions, to follow.

Various pigments may be used within the compositions of our invention.These include, for example, non-magnetics such as carbon black and zincoxide, and finely divided magnetizable particles, such as iron oxide,iron alloys, nickel alloys, ferrites, etc. These pigments, well known inthe art, impart a color characteristic to the composition, as Well as,in some cases, magnetic properties. These pigments are dispersed withinthe combination of resin, plasticizer and solvent.

We have found that various iron oxides ranging in size to an averageparticle size of 2 microns may be advantageously used within thecompositions of our invention. We prefer to use an alpha acicular ironoxide of an average particle size of one micron. One such material isknown as IRN-IOO, manufactured by C. K. Williams and Co.

The following table, Table II, represents some of the general andpreferred compositions within those ranges that we have discovered meetthe objects of this invention. It is to be noted that in most casesthere are but four constituents within each composition, and that allconstituents are entirely synthetic materials, which allows excellentquality control, without the variations normally found in naturalmaterials. Table II lists the compositions of our invention by ranges,and by preferred embodiment within each range.

TABLE II Preferred composition, pa 5 Parts by Wt. General materialsPreferred materials by wt 4.5-7.5 EAB-SOO EAB-SOO-l 7 8-15. Plasticizer.Glyceryl trioleate. 10 Pigment. Iron oxide 16. 5 Solvent. Methyl ethylketone 50 EAB-171 EAB-l71-2 5 Plastieize 10 Pigment. 16. 5 SolventN-propyl acetate 50 3-8 EAR-272 EAB-272-3 4. Plasticizer Dioctyl azelate14 Pigment-.- Iron oxide 16. 5 Solvent N-propyl acetate 50 5-8 Tenthsecond butyr- Tenth second butyr- 6. 5

ate. ate. 10-18 Plasticizer Dioetyl azelate 14 18 Pigment--. Iron oxide16. 5 Methyl ethyl ketone 40 EAB-381-1w- 6. 5 Dioctyl azela 12. 5 Ironoxide..- 16. 5 N-propyl acetate 50 5-8 Cellulose acetate pro-Half-second propio- 6 pionate. nate. 10-16 Plasticizer D ioctyl azelate12 igmen Iron oxide 16. 5 30-60 Solvent Methyl ethyl ketone- 40 5-8Alcohol soluble butyr- Alcohol soluble butyr- 6 ate. ate.

12 16. 5 40-80 Solvent- 60 The last single number following the vendordesignation of the resin represents the falling ball viscosity of thatresin. Thus, for example, EAB-SOO-l represents, by the numeral 1, aviscosity of 1 second.

Other pigments may be used in place of the preferred pigment, ironoxide, such as carbon black, iron alloys, etc.

The two most preferred compositions of this invention, used for magneticink transfer coatings, are as follows:

N-propyl acetate solvent Tenlo 7O surfacant Finely divided iron oxidepigment 16.5

These composition and those of Table II have been made and tested forenvironmental stability by placing them in temperature ranges from 20 F.to at least F. for a period exceeding five days, and then subjected toprint testing, which has shown no degradation of print quality over thistime period. This is in marked contrast to the temperature stability ofcurrent ink transfer compositions, shown in the prior art. Thistemperature stability thus results in a longer shelf life and greaterease of handling with image transfer mediums utilizing the ink transfercoating composition of our invention. This coating composition may beapplied thinner than compositions currently in use, due to thetemperature stability and uniformity of the compositions, thus allowingwinding a greater amount of a tape onto a given reel. Thus .25 milcoatings, instead of current .35 mil thick coatings, may 'be used. Theuse of all synthetic materials, which have greater parameter controlthan natural materials,

and the use of as few as four constituents, which allows greateraccuracy in mixing and blending, clearly allows better batch to batchuniformity. Further, these compositions, through temperature stabilityand uniformity of mixing, lessen peeling problems and flaking problemsfound in present print compositions. The increased temperature stabilityand uniformity of these compositions results in ribbons that exude verylittle oil, with the result that they are very clean to handle, and donot dirty the mechanical parts with which they come into contact in thecourse of use. The combination of the above helps result in improvedprint quality.

While coating compositions taught by our invention would most readily beapplied to one Side of a substrate, and transfer effected by impactingthe other side of the substrate, as in the usual typewriter or printsystem, it is clear that these compositions may be utilized wherever ahigh quality ink transfer coating composition is required.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

'1. A transfer sheet comprising a substrate having thereon the driedresidue of a coating composition consisting essentially of, in parts byweight:

3 to 8 parts of a resin selected from the group consisting of celluloseacetate butyrate and cellulose acetate propionate;

3 to 16 parts of a plasticizer comparable with said resin, selected fromthe group consisting of dioctyl azelate, glyceryl mono ricinoleate, andglyceryl trioleate;

40 to 80 parts of a solvent system capable of dissolving said resin,selected from the group consisting of N-propyl acetate, methyl ethylketone, and ethanol; and

13 to 18 parts of a pigment capable of being dispersed within saidresin, plasticizer, and solvent.

2. The transfer sheet of claim 1 wherein said pigment is finely dividedmagnetizable material.

3. The transfer sheet of claim 1 wherein said pigment is finely dividediron oxide material.

4. The transfer sheet of claim 1 wherein said composition includes asurfactant of the class consisting of fatty amides and polyethyleneglycol ester.

5. The transfer sheet of claim 1 wherein the resin is cellulose acetatebutyrate.

6. The transfer sheet of claim wherein said composition includes up to.25 part of a wetting agent of the class consisting of fatty amides andpolyethylene glycol ester.

7. The transfer sheet of claim 5 wherein said pigment is finely dividedmagnetizable material.

8. The transfer sheet of claim 5 wherein said pigment is finely dividediron oxide material.

9. The transfer sheet of claim 5 wherein the cellulose acetate butyrateis alcohol soluble butyrate and wherein the plasticizer is dioctylazelate and wherein the solvent is ethanol.

10. The transfer sheet of claim 9 wherein said pigment is finely dividedmagnetizable material.

11. The transfer sheet of claim 9 wherein said pigment is finely dividediron oxide material.

12. The transfer sheet of claim 5 wherein the cellulose acetate butyrateis tenth second butyrate, the plasticizer is dioctyl azelate, and thesolvent is methyl ethyl ketone.

13. The transfer sheet of claim 12 wherein said pigment is a finelydivided magnetizable material.

14. The transfer sheet of claim 12 wherein said pigment is a finelydivided iron oxide material.

15. A transfer sheet comprising a substrate having thereon the driedresidue of a coating composition consisting essentially of, in parts byweight:

5 to 8 parts cellulose acetate propionate;

10 to 16 parts of dioctyl azelate plasticizer;

30 to 60 parts of methyl ethyl ketone solvent;

13 to 18 parts of a pigment capable of being dispersed within saidresin, plasticizer, and solvent.

16. The transfer sheet of claim 15 wherein said pigment is a finelydivided magnetizable material.

17. The transfer sheet of claim 15 wherein said pigment is finelydivided iron oxide material.

18. A transfer sheet comprising a substrate having thereon the driedresidue of a coating composition consisting essentially of, in parts byweight:

6 parts cellulose acetate butyrate resin containing 13% acetyl, 37%butyryl, 2% hydroxyl, with a falling ball viscosity of substantially 0.5second;

12.5 parts of dioctyl azelate plasticizer;

16.5 parts of a finely divided iron oxide material;

50 parts N-propyl acetate solvent;

0.2 part of a wetting agent of the class comprising fatty amides andpolyethylene glycol ester.

19. A transfer sheet comprising a substrate having thereon the driedresidue of a coating composition consisting essentially of, in parts byweight:

7.0 parts cellulose acetate butyrate resin containing 13% acetyl, 37butyryl, 2% hydroxyl, with a falling ball viscosity of substantially 0.5second;

14.0 parts dioctyl azelate plasticizer;

1.0 part glyceryl mono ricinoleate plasticizer;

50.0 parts N-propyl acetate solvent;

0.25 part of a wetting agent of the class comprising fatty amides andpolyethylene glycol ester;

16.5 parts of a finely divided iron oxide material.

References Cited UNITED STATES PATENTS 3,062,676 11/1962 Newman et al.

FOREIGN PATENTS 947,219 1/1964 Great Britain.

MURRAY KATZ, Primary Examiner US. Cl. X.R. 106-26, '180; 11736.1, 138.8

